Niels Bohr

Summary

Bohr's Youth

Terms

Atomic energy -
· The energy generated from the splitting of the atom
(though nuclear fusion would later add further possibilities).

Bohr
atomic model -
· The Bohr model stabilized Rutherford's original picture
by showing that the atom could exist only in discrete energy states.

Complementarity -
· In light of the indeterminacy set forth by Heisenberg's uncertainty
principle, the principle of complementarity argues that two answers
are preferable to one when neither is itself complete.

Compound nucleus -
· A temporary excited state of the nucleus that occurs
upon the collision of two particles. Bohr postulated that the nucleus
might discharge this excess energy through the emission of radiation.

Copenhagen Institute -
· Founded and headed by Bohr, this Institute soon became
the world center for modern physics. Here Bohr cultivated new generations
of physicists, while hosting colloquia that would repeatedly alter
the course of history.

Correspondence principle -
· This principle states that a new theory must be applicable
to all phenomena for which a preceding theory was valid. It applies particularly
to theories at the atomic level, which had to be evaluated against
traditional phenomena as well, since classical physics had successfully
explained it.

Liquid-drop model -
· A theoretical model proposed by Bohr that compares
the nucleus to a drop of liquid. This model would later have consequences for
the discovery of fission.

Nuclear fission -
· A nuclear reaction in which the nucleus of an atom,
usually uranium, is split into two fragments, leading to the release
of a great deal of energy.

Quantum theory -
· A theory that addresses the duality of matter and energy,
which have the properties of both particles and waves. In creating
his atomic model, Bohr specifically applied Planck's idea that energy
consists of discrete packets called quanta.

Stationary state -
· A state of an atomic system that has a defined energy
level associated with it.

Uncertainty principle -
· Formulated by Heisenberg, this principle states that
the velocity and position of an electron can never be exactly determined, since
the act of measurement necessarily disturbs the conditions.

People

Aage Bohr -
Bohr's fourth son, who accompanied him to Los Alamos and became
his assistant before going on to his own career in theoretical
physics.

Christian Bohr -
Bohr's father, who was also a famous physiologist and Copenhagen
professor.

Ellen Bohr -
Bohr's mother.

Harald Bohr -
A
beloved brother of Niels, who remained a close companion and confidant
throughout their lives. Harald was also a distinguished mathematician.

Margrethe
Bohr -
Bohr's wife.

Albert Einstein -
Greatly admired by Bohr, Einstein was one of Bohr's
biggest critics. The two engaged in an endless debate that usually
centered on the principle of complementarity. Einstein's early
work also contributed to Bohr's atomic model.

Werner Heisenberg -
Early Copenhagen fellow responsible for the development
of quantum mechanics. He became most famous for his uncertainty
principle.

Hendrik Kramers -
Dutch physicist who would be a faithful assistant
to Bohr for almost ten years. He was pivotal in the establishment
of the Copenhagen Institute, and he remained a close friend for
many years, helping Bohr to campaign for international cooperation
on atomic policy.

Wolfgang Pauli -
Early Copenhagen fellow whose exclusion principle
addressed some of the shortcomings of Bohr's own electron theory.

Max Planck -
One of the early developers of quantum theory, Planck
postulated the existence of quanta, which would influence Bohr's
atomic model.

Ernest
Rutherford -
One of Bohr's first mentors,
Rutherford gave Bohr the direction he needed early on his career.
Bohr's atomic model was also largely a revision of Rutherford's
original. The two remained close throughout their lives.

Ernest Schrödinger -
Showed how electron behavior could be understood
in terms of waves. Schrödinger's theory yielded the same mathematical
results as Heisenberg's quantum mechanics, though their postulations
differed fundamentally.

J. J. Thomson -
Physicist whose work Bohr greatly admired, most known
for his discovery of the electron. Bohr went to Cambridge with
the hope of working with Thomson, but found him less interested
than he had hoped. He gave up on Thomson when the prospect of working with
Rutherford arose.